This invention relates generally to the field of petroleum production, and more particularly, but not by way of limitation, to an improved blender apparatus useable in well stimulation processes.
For many years, petroleum products have been recovered from subterranean reservoirs through the use of drilled wells and production equipment. Ideally, the natural reservoir pressure is sufficient to force the hydrocarbons out of the producing formation to storage equipment located on the surface. In practice, however, diminishing reservoir pressures, near-wellbore damage and the accumulation of various deposits limit the recovery of hydrocarbons from the well.
Well stimulation treatments are commonly used to enhance or restore the productivity of a well. Hydraulic fracturing is a particularly common well stimulation treatment that involves the high-pressure injection of specially engineered treatment fluids into the reservoir. The high-pressure treatment fluid causes a vertical fracture to extend away from the wellbore according to the natural stresses of the formation. Proppant, such as grains of sand of a particular size, is often mixed with the treatment fluid to keep the fracture open after the high-pressure subsides when treatment is complete. The increased permeability resulting from the hydraulic fracturing operation enhances the flow of petroleum products into the wellbore.
Hydraulic fracturing operations require the use of specialized equipment configured to meet the particular requirements of each fracturing job. Generally, a blender unit is used to combine a carrier fluid with proppant material to form a fracturing slurry. The blender unit pressurizes and delivers the slurry to a pumper unit that forces the slurry under elevated pressure into the wellbore. During the fracturing operation, it is important that the slurry be provided to the pumper units at a sufficient pressure and volumetric flowrate. Failure to generate sufficient pressure at the suction side of each pumper unit can cause cavitation that damages the pumper units and jeopardizes the fracturing operation.
Prior art blender units are subject to failure resulting from the inherent difficulties of preparing and pressurizing solid-liquid slurries. Blenders typically include pumps, mixing tubs and motors that are vulnerable to mechanical failure under the rigorous demands of high-volume blending operations. Accordingly, there is a continued need for a more robust blender apparatus that meets the needs of modem hydraulic fracturing operations.
The present invention includes a blender apparatus that can be used to prepare a slurry from carrier fluids and solids. In a preferred embodiment, the blender includes a mixing tub system, a fluids intake system, a solids intake system and a slurry delivery system. The fluids intake system preferably includes a first intake pump and a second intake pump that independently or cooperatively draw fluids into the blender. The slurry delivery system preferably includes a first discharge pump and a second discharge pump that independently or cooperatively deliver slurry from the mixing tub system.